1. Field of the Invention
The present invention relates to an apparatus for automatically measuring curvature of an object such as a cornea.
2. Description of the Prior Art
A similar apparatus is already disclosed in the Japanese Patent Laid-open No. 125302/1982. In such known apparatus, light from an annular light source is projected onto a cornea, and an oval image formed by the reflected light is received by a linear image sensor, and the curvature of the cornea is determined from the length of image sensor receiving said oval image. However such apparatus is associated with a drawback that an error will result in case the center of the oval image is not positioned on the image sensor. Also the Japanese Patent Laid-open No. 54927/1983 discloses another structure in which five image sensors are radially arranged to determine the oval shape and a rotating mechanism is eliminated in order to avoid the aforementioned drawback. However such structure is associated with a drawback of requiring a complicated electric circuitry and generating an error in case the surface of the cornea is not toric, since the principle of measurement is based on an assumption that the cornea has a toric surface.
Besides such conventional apparatus require a special annular light source.